A stopcock is usually hard to turn because it has not been used for a long time and limescale or corrosion has built up around the spindle and internal parts. A tight or dried-out gland packing around the spindle can also make it stiff, and in some cases the internal mechanism has started to seize.
A stiff stopcock should not be forced. Too much pressure can snap the handle or spindle, or start a leak, and leave you unable to turn the water off when you need to.
Why Stopcocks Become Stiff
Most people rarely touch their stopcock, sometimes for a very long time. Over time, minerals in the water can coat the moving parts, while metal parts can corrode where they meet.
The spindle passes through a gland that keeps water from escaping. The packing inside the gland can dry out or harden, gripping the spindle more tightly. Paint or debris around the handle can also add to the stiffness.
Why You Should Not Force It
It can be tempting to use pliers, a wrench or a length of pipe for extra leverage. Advice from WaterSafe, the national register of approved plumbers, says to avoid forcing seized parts and working on fragile or corroded pipework.
Forcing a stiff stopcock can shear the spindle, crack the body or damage the old pipe it is fitted to. That could turn a stiff valve into a leak that you cannot stop from inside the home.
Do not hit the valve or heat it either. If it does not move with normal hand pressure, leave it and get it looked at.
If you need to stop the water urgently and the stopcock will not move, the outside stop tap may be an option, but only if you can reach it and it turns easily.
What Can Be Done
In many cases a stiff stopcock can be repaired rather than replaced. Depending on its condition, a plumber may be able to loosen the spindle, renew the gland packing or replace worn internal parts.
Whether a repair is possible depends on how corroded the stopcock is, the type of valve and the condition of the pipe around it. If the body or pipework is badly worn, replacement may be the safer option, but that is not always the case.
Planning Ahead
Knowing that your stopcock works is useful before an emergency. If yours is stiff, it is better to have it checked while there is no leak, rather than finding out when water is pouring through a ceiling.
Once it is working again, some people choose to turn it gently a little each way every so often to keep it moving, as long as it turns freely.
If your stopcock will not turn without force, our stopcock repair service in Oxford can look at it safely and let you know whether it can be freed and repaired.